The present invention relates to a magnetic disk drive having a positioning mechanism of the type positioning a magnetic head relative to a recording medium in a rotaty motion, i.e., a so-called rotary positioning mechanism.
A magnetic disk drive of the type described is extensively used with a computer, word processor or similar electronic data processing equipment as a storage. There is an increasing demand for a magnetic disk drive capable of recording data in high density on a recording medium implemented as a disk. To meet this demand, it has been customary to increase the accuracy of the disk surface and to reduce the floating of the head above the disk. This, however, brings about a problem that the head is apt to sticks to the disk. In the light of this, a great current may be applied to a spindle motor which drives the disk or a voice coil motor which drives the head to thereby increase the driving force of the motor, as has been customary in the art. However, the great current for separating the head from the disk increases the required power and, moreover, often scratches the head and/or the disk since it forcibly separates the former from the latter.
On the other hand, a magnetic disk drive applicable to a lap-top type computer is powered by a battery. The prerequisite with this kind of magnetic disk drive is that it consumes a minimum of power and withstands shocks and impacts while being transported. Regarding the shocks and impacts, it is a common practice to increase the force which urges the head against the disk, so that the head may be prevented from hitting against the disk. The problem with this scheme is that the friction acting between the head and the disk increases to aggravate the power consumption of the spindle motor at the beginning of rotation of the disk. As a result, such a magnetic disk drive is not practicable with a lap-top computer. The head may be loaded onto and unloaded from the disk by mechanical means using a link, as proposed in the past. The mechanical head loading and unloading means, however, has a complicated and expensive structure and cannot be incorporated in a miniature magnetic disk drive. Further, the disk may be provided with a slant adjacent to the outer edge thereof to allow a suspension arm supporting the head to rise along the slant, as also proposed in the art. Such an implementation has a drawback that since the head moves obliquely relative to the disk, it cannot be accurately positioned relative to the disk.